Aboriginal languages may be much older than people think, argues a linguistic anthropologist who says they originated as far back as the end of the last ice age around 13,000 years ago.

This challenges existing thinking, which suggests Aboriginal languages developed from a proto-language that spread through Australia 5000 to 6000 years ago.

The key to the new hypothesis is prehistoric Australia's single land mass 13,000 to 28,000 years ago, when New Guinea and Tasmania were still attached, says Dr Mark Clendon in the journal Current Anthropology.

Clendon says the continent, known as Sahul, was relatively densely populated on the land bridge connecting northern Australia to New Guinea, now separated by the Arafura Sea.

The other populated area was along what is now Australia's eastern seaboard.

The eastern group spoke a tongue that became what is known today as Pama Nyungan and includes languages like Pitjantjatjara, Yolngu and Warlpiri.

And the Arafurans spoke another family of languages used in northern Australia today.

"What I'm suggesting is that Pama Nyungan and non-Pama Nyungan languages go back about 13,000 years to when there was a land bridge between New Guinea and Australia," he says.

Until now, the reason why these two Aboriginal language groups are so different, each with a distinct grammar and vocabulary, has been a mystery.

Climate change

Around 11,000 years ago what was the Arafura plain was flooded by rising seas as the ice age ended.

This caused the northern people to migrate into either New Guinea or to northern parts of Australia.

Meanwhile, increased rainfall and warmer temperatures made inland parts of the continent more habitable and sparked a westward migration of eastern dwellers.

This introduced their language group to more central areas of Australia.

Both groups maintained their distinct languages, Clendon says.

His hypothesis provides an alternative picture to the traditional view that 6000 years ago a single proto-language spread from the Gulf of Carpentaria around Australia, eventually giving rise to existing Aboriginal languages.

"We know about changes in climate and sea levels at the end of the Pleistocene era," Clendon says.

"I'm suggesting the way languages are configured in Australia today are a result of those changes that happened at the end of the ice age."

Provocative but unconvincing

Writing in a reply to Clendon's article, Professor Nicholas Evans, an expert in Aboriginal languages from the University of Melbourne, describes Clendon's hypothesis as "fresh and provocative".

However, he says there are flaws in the argument, including that there is only weak evidence of similarities between southern New Guinea and northern Aboriginal languages.

Evans says he remains to be convinced about Clendon's proposal.

"[But] it adds a welcome alternative to a field in which we are still a long way from having any clear picture of the unimaginably long human occupation of Sahul," he says.